feat(fe): Session timeout re-authentication dialog

[sea-snake]

After the 30-minute delegation expires, all dashboard requests used to fail with no way to recover.

Changes

• Re-auth dialog shown 5 minutes before delegation expiry, deferred if another dialog is open (force-shown at actual expiry).
• Re-authenticates via AuthLastUsedFlow with the current auth method, keeping the user on the same page.
• New ReauthPrompt component.

Tests

• Two Playwright e2e tests using page.clock to fast-forward: re-auth sign-in and cancel/sign-out flows.

[Copilot]

Pull request overview

Adds a front-end “session timeout” re-authentication UX on the authenticated Manage/Dashboard area so users can recover when their delegation expires (instead of dashboard requests failing indefinitely).

Changes:

• Adds a delegation-expiry timer in the authenticated manage layout to show a re-auth prompt ~5 minutes before expiration (with deferral while other dialogs are open).
• Introduces a new ReauthPrompt dialog component with “Sign in” and “Cancel” (sign out) actions.
• Adds Playwright e2e coverage for the re-authenticate and cancel/sign-out flows using page.clock.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
src/frontend/tests/e2e-playwright/routes/manage/index.spec.ts	Adds e2e tests covering re-auth prompt behavior and outcomes.
src/frontend/src/routes/(new-styling)/manage/(authenticated)/+layout.svelte	Implements expiry detection + deferred dialog presentation + re-auth action wiring.
src/frontend/src/lib/components/ui/ReauthPrompt.svelte	New UI component for the session timeout re-auth prompt.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[aterga]

Testing that this works as expected on Staging B.